System.Data.DataTable.ShadowIndexCopy C# (CSharp) Method

        internal void ShadowIndexCopy()
        {
            if (_shadowIndexes == _indexes)
            {
                Debug.Assert(0 < _indexes.Count, "unexpected");
                _shadowIndexes = new List<Index>(_indexes);
            }
        }

        public void AddRef()
        {
            Bid.Trace("<ds.Index.AddRef|API> %d#\n", ObjectID);
            LockCookie lc = table.indexesLock.UpgradeToWriterLock(-1);

            try {
                Debug.Assert(0 <= refCount, "AddRef on disposed index");
                Debug.Assert(null != records, "null records");
                if (refCount == 0)
                {
                    table.ShadowIndexCopy();
                    table.indexes.Add(this);
                }
                refCount++;
            }
            finally {
                table.indexesLock.DowngradeFromWriterLock(ref lc);
            }
        }